Method of making plastic polystyrene



Patented Feb. 8,

v METHOD OF MAKING POLYSTYRENE John W. Church, Mount Lebanon,

Falk & Company, 01 Pennsylvania ENT QFFICE Pa., assignor Carnegie, Pa.,a corporation No Drawing. Applicatlon August is, 1944,

- Serial No. 549,033 I n Y 2 Claims. (01. 260- This invention relates toprimarily styrene plastic masses.

The object of the invention is to produce plasticmasses in whichparticles of macromolecular structure are obtained by reacting styrenein the presence of a protein, and are recovered in association with aplasticizing material therefor.

In accordance with my invention, monomeric styrene is heat-reacted in anaqueous emulsion which serves as polymerization proceeds to formmacromolecular bodies in particulate form. Following the formation oisuch macromolecular structure an aqueous suspension of physicalparticles formed of such structures is obtained. In

accordance with my invention there is added to sucn aqueous suspension asuitable plasticizing material for the reaction product and a primarilystyrene plastic mass comprising the reaction proda method of making notand the plasticizer is formed and recovered.

In accordance with my invention I prepare a water emulsion, using aprotein as the protective styrene and capable of holding the reactionproduct in a finely particulate form.

My invention may be=.;more specifically exemplified as follows:

Example 1 In this exempliflcation of my invention I added 30 parts byweight of Alpha-protein (glycinin from soya beans) to 100 parts byweight of water in a steam jacketed vessel equipped for refluxing. Thewater was brought to its boiling point of approximately 210 F.. suchtemperature elevation desirably being efi'ected before the Alphaproteinwas added. I then added sodium tetra borate as a peptizer for theprotein and stabilizer for the emulsion. The liquid was agitated afteraddition of the sodium 'tetraborate until it was smooth.

To the emulsion as above formed I added 100 parts by weight of water atlower temperature and then slowly added 3'75- parts by weight ofmonomeric styrene in condition for polymerization. With the monomericstyrene there was included benzoyl peroxide in a weight equal to .296

persion so obtained is .ing to dry the material into a powder.

associated with the the weight of the styrene. agitated until smooth andabout 900 parts by weight of water were added. The temperature 01' thereaction mixture was slowly raised during a period of about 45 minutesuntil a temperature of about 180 F. was reached, and there was then arapid exothermic rise in temperature accompanied by some refluxing andrapid thickening of the mixture. .Upto this point the reaction mixturehad been agitated but when thickening occurred agitation wasdiscontinued.

The reaction mixture was then placed in drums equipped for reflux and F.1'01 48 hours. At that time the reaction mixture consisted of a verythin liquid in which hadsettled a spongelike formation'which could .bedisintegrated into A substantially homogevery small particles. neousaqueous suspension was made by passing the sponge-like formation of thereaction product together with the liquid from which it had separatedlightly through a stone mill. The smooth substantially homogeneousaqueous disvery diflicult to flocculate.

It is also extremely difiicult, if not impossible to wash out the lasttraces of entrapped protein.

Also it appears impossible, except by spray dry- It' is. however,possible to ticizer as a plastic mass.

As exemplary of the recovery stages 01' my process the aqueousdispersion was introduced into a heavy internal mixer and aplasticizingmaterial for the particulate product wasadded.

' "The aqueous dispersion and plasticizer were heated gently to atemperature'of about F. and were mixed until the plasticizer became soparticles that there was formed a plastic mass from which the water maybe removed by decantation and evaporation.

The aqueous suspension made specifically as above described consisted ofabout 35% solid particles and to this suspension there were added 30parts by weight of methyl stearate to each 100 parts of solid material.This, when dry, produced a very tough elastic mass capable of forming aself-supporting film, Y

This product being capable Of moderate flow under heat andpressure andsubstantially free from cold-flow, is a good material for joint caulkingand for laminating. It is capable both of extension and bi deformationunder compressive force, and has reasonably good elastic recovery underboth.

This mixture was 9 was maintained at. a temperature of F. to 200 recoverthe particulate re-- action product associated with a suitable plas- Infurther exempliiication of my inveutim. the following may be given; V

trample 2 The procedure of Example 1 was duplicated exactly, except thatin making the protective colloid 35 parts by weight of casein was used,instead of 30 parts by weight of glycinin. to 100 parts by weight ofwater. The plastic mass recovered was in its properties identical withthe plastic mass recovered in Example 1.

The reason for using a somewhat greater proportion of casein in theprotective colloid is that casein tends to give a thinner emulsion thanis given by the glycinin, Alp "-protein.

In making the initial emulsion, the proportion of protein to water whichisused depends on the sort of protein and the conditions or the process.

It is necessary that the protein be such that it gives a smoothprotective colloidsolution when agitated with water and a peptizer, thatsuch protective colloid be capable of dispersing the monomeric styrenefor the reaction by which bodies of high molecular weight are formed,and that it be capable of thickening sumciently as the reaction proceedsto maintain dispersion of the reaction product. This coniunction ofproperties is possessed by casein, and by its substantial equivalentglycinin. It will be observed in the examples that the relatively thinemulsion retains its desired fiuidity to a stage at which thepolymerization reaction begins, and thereafter thickens. The above factapplies to the proportioning. of protective colloid to styrene, theprepared protein emulsion being capable of dispersing a relatively greatproportion of styrene in the reaction liquid, fluid at normal roomtemperature. It is not possible to give specific proportions because ofthe many variables involved, such as the condition oi" the availablecasein or glycinin at the time of. its use, and the purity andreactivity of the monomeric styrene liquid. This explanation will,however, permit practice to' be based satisfactorily on'the exampleswhich have been given. with such variance therefrom as the condition ofthe materials used and a general knowledge of the art will dictate.

The primary fact as to the formation of the protective colloid and theemulsification of the monomeric styrene is that the proteins casein andglycinin have the property of'making with the monomeric styrene suchdispersion of the styrene that particles of very high molecular weightstructure are formed and are prevented from coalescing in a reactionemulsion which is sufllciently thin for satisfactory handling until thereaction has been started. I am not aware whether or no the protein ischemically involved with the styrene in forming micellular structures ofhigh molecular weight, or whether its function is primarily one of socarrying and presenting mon-' omeric styrene that the contact efiect isparticu larly favorable to the building of macromolecular bodies.Whatever the mechanism may be, the result is the formation of geledmasses when the reaction product is mixed with plasticizer.

It is well known that monomeric styrene not only polymerizes violentlyto polystyrene of high average molecular weight under moderate heatingbut that an auto-polymerization normally takes place in a body ofmonomeric styrene at normal room temperature. For this reason there isnormally associated with commercial monomeric styrene a suitablepolymerization inhibitor in the form of a reducing agent such asanthrasirably are dissolved in the styrene before it is added to theprotective colloid. In the event that the starting material is freshlydistilled monomeric styrene containing no polymerization inhibitor theuse of an appropriate counter agent is unnecessary in forming highmolecular weight 1 heat polymers of the styrene.

step is also a recovery step; inasmuch as the addition of theplasticizer facilitates the recovery of the fine suspended particles ofreaction product by including-themin the desired plastic mass. 0 Methylstearate has been given above as the recovery plasticizer ofthe'particulate mass. Any

- other oily, non-volatile plasticizer of good solvent power may beused. Thus methyl stearate is exemplary of the class of alkyl esters oflong chain acids. Of the other suitable classes of plasticizers theremay be given the aromatic hydrocarbon plasticizers, as exemplified bycoumaroneindene dimer oil; the plasticizers which are esters of aromaticacids. such as dibutyl phthalate; chlorinated aromatic hydrocarbonplasticizers, such as chloro-benzene; and chlorinated aliphatichydrocarbon plasticizers, such as chlorinated parafiin.

The proportion of plasticizer to solid resin desirably used will dependin each instance on the solvent power of the 'plasticizer, themacromolecular reaction product being of approximately uniformly highmolecular weight, and the desired consistency of the recoveredpolystyrene mass.

4 Thus with the proportion of methyl stearate given, the mass has suchtensile strength that it may be-sheeted or calendered into aself-supporting film. If less of that plasticizer is used the materialis stiller and may be used for molded and extruded plastics; and if moreis used the material is softer and more pliable. It is a simpleadjustment to obtain analogous results by using a smaller proportion ofa plasticizer of greater solvent power.

where parts and proportions are given above without qualification. theyare to be taken as parts and proportions'by weight.

It is to be understood that I do not intend to limit myself to thespecific description and ex- 55 emplifications of my inventionhereinabove given in disclosing and embodying that invention. nor to thespecific terms used in so doing, and that my invention is to berestricted only by the limitations placed thereon by the claims appendedhereto.

I claim as my invention:

1. The method of making plastic masses by subjecting monomeric styrenein reactive condition to heat reaction in water emulsion with aprotective colloid formed by a protein selected from the group ofproteins consisting of casein and glycinin, continuing heatpolymerization until a solid sponge-like reaction product ofmacromolecular structure comprising high polymers 70 of styrene andprotein of the colloid forms and settles in the reaction liquid. forminga fine aqueous suspension of the said separated reaction product bymilling, and recovering the said finely particulate reaction productirom the said q eous suspension in a plastic mass by admix- It will havebeen noted that the plasticizing ture 01' a non-evapo'rative solventplasticizer and removal of water. 7

2. The method of making plastic masses by subjecting monomeric styrenein reactive condition to heat reaction in water emulsion with aprotective colloid formed by a protein selected from the group ofproteins consisting of casein and glycinln,- continuing the heatpolymerization in the emulsion until a solid sponge-like reactionproduct of macromolecular structure comprising high polymers of styreneand protein of the colloid forms and separates from the reaction liquid,bringing the said separated reaction product into fine aqueoussuspension, and recovering the said reaction product from the saidaqueous suspension in a plastic mass by admixture of a nonevaporativesolvent water.

plasticlzer and removal of JOHN w; CHURCH. REFERENCES CITED Thefollowing references are of record in the file of this 'patent:

Number UNITED STATES PATENTS Schoenfeld Apr. 10, 1945

